Egbert m



(No-Model.)

Patented Apr. 25,1882.

MM w o a m UNITED STATES PATENT OFFICE.

ROBERT M. LOOKVOOD, OF NEW YORK, N. Y., ASSIGNOR TO THE MOLECU- LAR TELEPHONE COMPANY, OF SAME PLACE.

RECEIVER FOR TELEPHONES.

SPECIFICATION forming part of Letters Patent No. 256,907, dated April 25, 1882.

Application filed September 10, 1881. (N model.)

To all whom it may concern: I

. Be it known that I, ROBERT M. LOCKWOOD,

of the city, county, and State of New York,

haveinvented new and useful Improvements in Receivers for Telephones, of which the following is a full, clear, and exact description, reference being bad to the accompanyingdrawings, making part of this specification, in which- Figure l is a side elevation of myimproved receiver, partly in section, showing the arrangement of the diaphragm, &c.; and Fig. 2 is a plan or face view of the diaphragm.

My invention relates to an improvement in diaphragmstor telephone-receivers and itconsists in making such diaphragms of cork or equivalent non-resonant and nonmagnetic material, provided with a central button of carbon or its cquivalent,forming'a hard, rasping, and non-magneticwear-plate for the reduced extension or rccurved arm of the magnet to rest and act upon, as hereinafter explained.

The receiver in its organization or arrangement of parts maybe similar to that described in Letters Patent granted to Lockwood and Bartlett June 15, 1880,No. 228,855 or it may be made in any usual or preferred form, so long as the magnet employed therein is provided with a yielding or reduced extension resting in contact with the diaphragm.

The body of the diaphragm (indicated at A) is made of cork or some equivalent non-resonant or non-magnetic material, and by preference is made in the form of a central disk, A,

with a ring, A, of similar material, surrounding it, and secured in place by means of thin elastic overlapping rings in a manner described in another application of even date herewith.

The diaphragm has a central perforation formed in it, in which is secured a small disk or button,B, of carbonor some equivalentnonmagnetic material-such,for instance, as pumicehavin g a gritty or rasping substance or nathis reason I prefer to apply it in the central v Patent, is-

perforation in the latter when the cork has been softened and rendered yielding by steaming or otherwise, when the button can be forced into place, and the cork being afterward dried under pressure, the carbon button will be firmly and securely held in place therein without the aid of glue, cement, or other fastening which would separate it from the cork. By this arrangement of central button or disk a hard non-magnetic conductor and wear-plate is interposed between the yielding. extension of the magnet and the cork, and disturbances in the current or in degree of polarity in the magnet may be imparted to the cork with greatly-increased intensity, adapting them to be much more casily and distinctly recognized by the ear.

Having now described my invention, what I claim as new, and desire to secure by Letters In a telephone-receiver, a diaphragm of cork, provided with a central button of carbon or its equivalent, applied thereto substantially as specified,in combination with the magnet having the reduced elastic extension restingin contact with said button, substantially as and for the purpose described.

In testimony whereof I have hereunto set my hand this 9th day of September, A. D. 1881.

ROBT. M. LOOKVVOOD. Witnesses:

Gno. BELL, OHRIs. SCHULTZ. 

